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Direct evidence of a near-ideal Jeff=1/2 ground state in triangular-lattice Na2BaCo(PO4)2

M. M. Ferreira-Carvalho1,2, S. H. Chen1, Y. C. Ku3,4, Anagha Jose5, Ryan Morrow5, C. Y. Kuo3,4, C. F. Chang1, Z. Hu1, M. W. Haverkort6 et al.

L. H. Tjeng1

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Phys. Rev. Materials 10, 025004 – Published 26 February, 2026

DOI: https://doi.org/10.1103/65bn-63kj

Abstract

We investigated the local Co 3d electronic structure of Na2BaCo(PO4)2 using polarization-dependent x-ray absorption spectroscopy (XAS) in combination with full multiplet cluster calculations. We employed the line-fitting inverse partial fluorescence yield (IPFY) technique to obtain accurate XAS spectra from strong insulating materials. Our combined experimental and theoretical analysis reveals a very small effective trigonal distortion of only 11 meV in the CoO6 octahedra, indicating a close to ideal condition to render a ground state with the Jeff=1/2 character. With our cluster model we were also able to simulate magnetic susceptibility measurements along different directions in the crystal. These findings highlight Na2BaCo(PO4)2 as a promising platform for exploring exotic magnetic phenomena associated with Jeff=1/2 ground states on triangular lattices.

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Phys. Rev. Materials 10, 025004– Published 26 February, 2026
  • Received 3 November 2025
  • Accepted 5 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by Max Planck Society.

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